Most of current mesh routing protocols use the minimum hop count as the metric to make path/route selection decisions. As used herein “/”, denotes alternative names for the same or similar components. With this approach, the quality of radio links, the traffic load and the available bandwidth of the links are not considered. The route with the minimum number of hops is selected to forward the data, which is in the form of packets or frames. However, minimal hop count routes can have poor performance because the routes tend to include radio links between distant nodes and the quality of links along the route may not be good. Radio links with a long physical span can be lossy, incurring a number of retransmissions and a low physical layer data rate. Many radio transmission systems, for example IEEE 802.11 and IEEE 802.16 radios, adapt the physical layer data rate depending on the link quality. This actually results in poor throughput and reduces the efficiency of network utilization compared to selecting a path with more hops but better link quality.
In the prior art, a metric called “expected transmission count” (ETX) has been used as a routing metric. The ETX estimates the expected number of MAC layer transmissions needed to successfully deliver a packet through a wireless link. The route with the lowest sum of the ETX's of all links along the path (the path with the lowest ETX cost) is selected. The ETX captures the effects of packet loss rates of a link but does not take different transmission rates and the available bandwidth of the links into account.
In another reported prior art scheme, a metric called “expected transmission time” (ETT) has been proposed to improve the ETX by considering the difference of link transmission rates. The ETT of a link is defined as the expected MAC layer duration for a successful transmission of a packet over the link. The cost of a route is the sum of the ETT's of all links along the route. The ETT takes the impact of different link transmission rates into account. However, it does not fully capture the impact of the traffic load and the available bandwidth of the link as well as the interference in the networks due to the shared medium. A heavily loaded link may be selected to include in the route so that these links become more loaded and the congestion occurs.
In a previous related application, a weighted radio and traffic load aware (WRALA) routing metric was described. The described metric captures the impact of various aspects of a wireless link in mesh networks, including the radio transmission rate, loss rate, traffic load and available bandwidth of the link as well as the interference due to the shared medium in the networks.
However, none of the above routing metrics consider the impact of multi-radio multi-channel on the routing performance. In a mesh network, a node/mesh point may be equipped with multiple radios and each of the radios can operate on a different channel/frequency to enhance network capacity. Unlike a node with a single radio, a multi-radio multi-channel node can receive data packets on one channel and simultaneously transmit data packets on another channel. It is, therefore, preferable to select a relay node with multiple radios each radio operating on a different channel. Furthermore, even with a single radio, a node having a radio that can operate on multiple channels may receive data on one channel and then switch to another channel to forward/relay/transmit the data.
It would be advantageous to have a system for selecting a route for data to traverse a mesh network that uses a metric that is not only traffic and bandwidth aware but also captures the impact of having one or more nodes having multiple radios, each radio operating on a different channel, or where one or more nodes have a single radio operating on multiple channels